Lumbar muscle atrophy and increased relative intramuscular lipid concentration are not mitigated by daily artificial gravity after 60-day head-down tilt bedrest

De Martino, Enrico, Hides, Julie, Elliott, James M., Hoggarth, Mark, Zange, Jochen, Lindsay, Kirsty, Debuse, Dorothee, Winnard, Andrew, Beard, David, Cook, Jonathan A., Salomoni, Sauro Emerick, Weber, Tobias, Scott, Jonathan, Hodges, Paul W. and Caplan, Nick (2021) Lumbar muscle atrophy and increased relative intramuscular lipid concentration are not mitigated by daily artificial gravity after 60-day head-down tilt bedrest. Journal of Applied Physiology. ISSN 8750-7587 (In Press)

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Official URL: https://doi.org/10.1152/japplphysiol.00990.2020

Abstract

Exposure to axial unloading induces adaptations in paraspinal muscles, as shown after spaceflights. This study investigated whether daily exposure to artificial gravity (AG) mitigated lumbar spine flattening and muscle atrophy associated with 60-day head-down tilt (HDT) bed rest (Earth-based space analogue). Twenty-four healthy individuals participated in the study: Eight received 30 minutes continuous AG; eight received 6x5 minutes AG, interspersed with rest periods; eight received no AG exposure (control group). Magnetic Resonance Imaging (MRI) of the lumbopelvic region was conducted at baseline (BDC) and at day 59 of HDT (HDT59). T1-weighted images were used to assess morphology of the lumbar spine (spinal length, intervertebral disc angles, disc area) and volumes of the lumbar multifidus (LM), lumbar erector spinae (LES), quadratus lumborum (QL), and psoas major (PM) muscles from L1/L2 to L5/S1 vertebral levels. A chemical shift-based 2‐point lipid/water Dixon sequence was used to evaluate muscle composition. Results showed that: spinal length and disc area increased (P<0.05); intervertebral disc angles (P<0.05) and muscle volumes of LM, LES, and QL reduced (P<0.01); and fat/water ratio for the LM and LES muscles increased (P<0.01) after HDT59 in all groups. Neither of the AG protocols mitigated the lumbar spinal deconditioning induced by HDT bed rest. The increase in lipid/water ratio in LM and LES muscles indicates an increased relative intramuscular lipid concentration. Altered muscle composition in atrophied muscles may impair lumbar spine function after body unloading, which could increase injury risk to vulnerable soft tissues. This relationship needs further investigation.

Item Type: Article
Uncontrolled Keywords: Short-arm centrifugation, paraspinal muscles, immobilization, magnetic resonance imaging
Subjects: B900 Others in Subjects allied to Medicine
C100 Biology
C600 Sports Science
Department: Faculties > Health and Life Sciences > Sport, Exercise and Rehabilitation
Depositing User: John Coen
Date Deposited: 09 Jun 2021 12:27
Last Modified: 09 Jun 2021 12:46
URI: http://nrl.northumbria.ac.uk/id/eprint/46395

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